Mixing mill



R. w. ALLEN Oct. 14, 1941` MIXING MILL l Filed Sept.l 29, 1959 4Shee'bS--Sl'xeeiI 1 s Y E N R O T T A R'. w. ALLEN MIXING MIL'L Oct. 14,1941.

Filed Sept. 29, 1939 4 Sheets-Shee'kl 2 ATTORNEYS R. W. ALLEN MIXINGMILL Oct. 14, 1941.

4 Sheets-Sheet 3 Filed Sept. 29, 1939 llll INVEN-ro @7mo/VD W. LL EN EIl. lll

Oct. 14, 1941. I l R. w. ALLEN y 2,259,058

' MIXING MILL Y Filed Sept. 29, 1959 4 Sheets-Sheet 4 RIGHT END LEFT54m/85 swI-rcH ATTORNEYS /05 f Patented Oct. 14, 1941 U NI TE D! Thisinvention relates to mixing millsor'stli mixing or warming ofplastic;materia1::.suchras.- rubber composition-:and more ,especially it're-1.r4 lates to' automaticallyV operating millswhereinia 1 blademoving relativelyiofbnef: theimill-frolls 5 eiects the strippingg'ofi a.sheet 4of.p1asti'c :magA terial therefrom andthefeedin'g oft'th'e-fstrippedfa' material back into the biteofJthe rollsxwherebyV optimummixing-.or Warmingof; the plastic lcomA positionvis eiected.

In apparatus of .the charactenmentioned; ase` heretofore provided', theblade: has been. moved f? into and out of engagementmith .the-'millroil.v by-means of a fluid pressureioperated, cylinderf the latter beingmountedrupon. a Vcarriages.that15 has a reciprocatorymovementlongitudinally off the ymill roll, 1 a Vreversible electric:motornb'eingi; employed for moving :the carriage.; Reversing: switchesVat the ends of the:carriagestraverse:

and" Valve-operating;Y mechanisms .-usu'ally were positioned Yalong thecourse of 'the' i carriage for: operating the fluid' pressure Acylinder?carried thereby.

Videfan improvedrmixing: mill ibi the :character mentioned wherein; the'use of .uid vpressure1oper^"Y -v ated cylinders is obviated;.tonnobviate the use of aplurality of valves such aszarernecessary;withf:

motor driven-means for efEe'cting.;th'e:-.raising andff lowering ofthescraperbladeiofithemillito prof-L vide. means i for yieldingly applying:thescrap'ev blade to a mill roll; and to provide automatically* Figure 7'isga VdiagrammaticLview. showingfthel course.ofithescraper;:b1a:deL

Figuresz; '9,';and loare idetail"elevations-eta pair Lof zswit'ches; andtheirs operating.; means, as viewedfrom theline ofFigurei, 1in various;

phasesaof a cycleeof operation-of the^fapparatusand g' l Riguresfll; l2;13, and V14'aredetail elevations,

of anotherl'fswitchfand lits operatinggzmeans; as f viewed 4:from theleftofrFigures 1; and 4; shown@v in :differentl phases of: a. cycle ,ofpperation-ofz-the apparatusa;

Referring now to the drawings, especially Figuresl and.; 2`there0f',1ther e-is shown' fa Vfrubber'hworking:millfjcomprising;endgf'framesfl 0, I U: in;- which are@yjournaledc-[a vpair rof :-laterally ,disp osed horizontal' ro-11s 1I I;i I 2, that lare: geared :together f and :driven in: unisonzbygthe usual:drivingfmeans (notishowmr The rolls ;II,` I2-are adapted. to-` usuauywere provided for:l reversing;'1;hem0t;4;)r;V 20 'fornrrav sheetorsleeve I3 of plasticrcompositionj from a: rbank' LI 4 "offsuchfcomposition that is 'fed intoth'e -bite-between'said rolls, ,the-sheetISbe` I ing: shojwuh'ereiny asaform'edgon the front-roll'. lI 2-.

Asshown, the millfis :associatedi'with a=super The chief objects of the;invention arestocpro:` 2! posed;B8Jnbury='miXerfofwell'knownconstrucftion V:wherein the l,various-constituent ingredients roff agbatch of-`rubber composition initiallygareras-,I

sembled and coo-mingled; the arrangement being; such thatthebatchfmaygbedischarged-from the uidl pressure Operated papparatus;gxtoiprovide'ifibottom offtheBanbury3 'and-olirectly; receivedinl which :isdesignatedas-a -whole by' the;numeral I d0, comprises respective hollowendfhousings .I 5; I 5A that; are fsuperposed upony the respective endoperated switch means for operating. theelectri'c-- Sgwframesil of the-mi11.- Of course,11;he fqgalnlmlryy allyrdriven mechanism of. the'apparatus 1in dei-1 terminate time sequence.v Otheri objects will Ibex--manifest as the description'proceeds;hv

Of the yaccompanying drawings:

Figure 1 is a front elevation of. apparatus em'- 40 bodying theinvention, .parts'bei-ng broken 'away' to reveal underlying mechanisms;`Figure 2 is a section, onta largerisca-le, on the line' 2-2 of Figure l,some parts beingshownfzirrf elevation; l v

Figure 3 is a sectionronfthelinei\3-3 rof Figl-L ure 2; I

Figure 4 is a sectional detail :ViewA On'th'elme' 4-#4 ofl Figures 1 and6,parts b'eingshown in;`

elevation;

Figure 5 is a fragmentary sectional View on the. line 5--5 of Figure 6;

Figure 6 is Van end elevationmof the-.electric switchesV and theiroperating mechanism as viewed from the left ofjFiguresl and 4;-,

portion ,ofi the; milli rmay';be'omitted,if :desired:

Mounted uponA the confronting-2 walls,` Lof.: the. end housings `I 5,' I5,.' .finteriorly .of the v'said :end L housingsrf'are bearinglplates-I8; lgtheiforme-r being inJ-the.end-housingw at the-left end-of, themillas---viewed in Figure l,A and-the-latter: beingJV in the end' housing-at the right end lof" the/mill.y

The r-wallA of' each housing Istructure'y I 5; backof- `the bearingplates I 8,1" I 9,;isV apertured to receive a pair 4ofvertically'aligned-g annular, 'apertured sockets 20; 2IJl that.' areVformecllonthe` rearv face.

of each'bearing-plate, the sockets-Ici one bearing plate -being`axially; aligned. with the sockets L off 1 50. the,.other. 4. Received.-in. :said f socketsf.. 2 0 yare the.

reducedvend Vportions offra 'pair of-.parallel;'horizontal guide barsorshafts 2 I, 2I,'saidguidebarsbeing-4 disposed in fthe same,verticalplane above f Threaded through the nut 40 is a feed screw 59,the same having threads thereon for about twothirds the distance fromits upper end, the lower third of the screw being smooth, there being aflange 5| formed at the juncture of the threaded and the smoothportions, said smooth portion projecting through the open lower end 0fthe carriage structure. The arrangement is such that rotation of the nut40 will cause the feed screw 50 to move axially up or down according tothe direction of rotation of the nut, the hollow extension 31 of theupper housing 36 receiving the through suitable apertures in confrontingwalls of the end housings I5, the left end of the feed screw beingjournaled in a bearing25, Figure 4, carried by the bearing plate IB. endof the screw 24 is journaled in a suitable bearing carried by thebearing plate I9, and has a terminal portion that projects beyond saidbearing and is provided with a gear 26 thereon. The latter is in meshwith a pinion 21 mounted upon the shaft of a reversible motor 28, Whichmotor is supported upon a bracket 29 afxed to the bearing plate I9. Theratio of the pinion 21 to the gear 26 may be varied to obtain thedesired mixing speed, or the motor 28 may be of variable speed. Accessto the motor 28 is had through an aperture 30 in the outer wall of thehousing I5, which aperture is provided with a cover plate 3|. The motor28 is driven alternately in opposite directions, and control means forreversing the direction of rotation of the motor presently will bedescribed.

The carriage 22 is a hollow structure comprising a rearwardly disposedbearing bracket portion 33 that engages the slide bars 2 I, and atransversely arcuate cover plate 34 on the front thereof. The structureis open at top and bottom, and mounted in its upper opening is a lowerhousing 35, and mounted upon the latter is an upper housing 36, thelatter being formed with a tubular l axial extension 31 that extendsupwardly and is closed at its-upper end. The lower housing 35 carries anaxially disposed bearing 38 and the upper housing 36 carries an axiallydisposed bearing 39, said bearings rotatably supporting a nut 49 byengagement with opposite end portions thereof. Mounted upon the exteriorof the nut The right hand- 4D is a gear 4I that is meshed with a pinion42, Y

the latter being mounted upon the lower end of the shaft 43 of a motor44. Said motor is supported upon the tubular extension 31 of upperhousing 36, the shaft 43 extending through said housing. The motor 44 isreversible, and is supplied with electric current through athree-conductor cable 45 that extends from said motor to a trolleycollector 46 that is supported upon the carriage 22, directly above theupper guide bar 2|. Said trolley collector is positioned within atrolley duct 41 that is mounted upon the bottom of the Banbury structureI4, said duct being open at the bottom to enable the collector 46 tomove longitudinally thereof. The trolley collector and duct are ofwell-known construction, and are arranged to supply electric current tothe three conductors of cable 45 at all positions of the carriage 22.Control means for reversing the direction of rotation ofthe motor 44according to the position of the lcarriage in its traverse of the millis included in the circuit of motor 44 and presently will be described.The said motor circuit also includes :a torque-limit relay (not shown)that serves to disconnect the electric current thereto when thedrivingtorque exceeds a determinate maximum limit.

screw when it is moved upwardly. Formed in the bracket portion 33 of thecarriage, along the parting plane thereof and its cover 34, areoppositely disposed, parallelslideways 52, 52, Figure 3, in which aslide 53 is mounted for sliding movement parallel to the screw 50. Theslide 53 is mostly of transversely arcuate shape so as to extend aboutthe screw 50 in spaced relation thereto, but intermediate the upper andlower ends of the slide there is formed a forwardly projecting ledge orshelf 54 through which the smooth lower end portion of the screwextends, there being a bushing 55 in said shelf about the screw toreduce friction as the slide and screw move relatively of each other.Mounted upon the smooth end portion of the screw 50 in abutting relationto the flange 5I is a collar 56, and mounted upon said screw betweensaid collar and the ledge 54 of the slide 1s a compression spring 51,the latter being encased at its lower portion in a protective sleeve 58.Mounted upon the front of the slide 53 at the lower end thereof is ablade holder 59 that has limited adjustability in an up and downdirection, the upper margin of said holder abutting a pair of set screws6U, 69, Figure 1, that are threaded into the overhanging ledge 54, andwhich assist 1n retaining the holder in adjusted position againstpressures to which it is subjected during use. A scraper blade 6| issecured to the front face of the holder '59, the lower margin of saidblade constituting a cutting edge that extends below the bottom of saidholder, in position for engagement with the mill roll I2. The bladeholder '59 is formed with a central slot 62 extending downwardly fromits upper margin, and the holder 53 is recessed behind said slot, asshown 1n Figure 1, to receive a slide block 63 that is mounted upon thelower end of screw 50, said block being slidable in said slot 62 and insaid recess behind the same. The end of screw 5D is squared to receivesaid slide block, the arrangement being such that rotation of said screwis prevented, yet axial movement of the screw relatively of the slide ispermitted. Thus downward movement of the screw 50 also moves the slide53 downwardly until the blade 6| engages the mill roll l2, furtherdownward move ment of the screw before stopping resulting in compressionof the spring 51. The latter assures more even pressure of the bladeagainst the mill roll notwithstanding unevenness of the surface of saidroll. It also serves to increase the driving torque of the motor 44,which torque ultimately effects the automatic stopping of the motor.

As previously stated, the reversible motor 28, by driving the screw 24alternately in opposite directions, impels the carriage 22 back andforth longitudinally of the mill rolls II, |2, and the reversible motor44, by alternately driving the nut 40 in opposite directions, raises andlowers the screw 50 and with it the scraper blade 6|. These operationsare effected in determinate time relation and impart to the scraperblade a compound movement that causes it to traverse a course that isdiagrammatically illustrated in Figure 7. From this figure it will beapparent that as the movement, of the blade carries it toward the end ofthe roll, it is lifted from the roll for a brief interval, vand thenlowered `into engagement with the roll before the end of the latterisreached. Upon reaching theend of the roll the direction ofv lateraltravel of the blade is reversed andl it moves; toward the opposite endof the roll while still engaged therewith, and upon approaching theopposite end ofA the roll is again lifted oif the roll and again loweredinto engagement therewith, in the same manner as previously described.When the blade 6| is moved toward the roll |2, near the end of the roll,itforces and cuts its way through the sheet of material I3 thereon.'IThen as its direction of lateralf movement is reversed and it movestoward the oppositeend `of the roll it forces its way through 'the sheetI3 and piles it up somewhat at its leading edge, as is best shown inFigure 1, and lays the stripped material in convolutions or folds thatare disposed' obliquely of the roll. When the blade'subsequently rises,the fold ofstripp'ed material passes substantially lengthwise into thebite of rolls |I, I2 whereby intimate mixing and warmingof theingredients thereof is effected. ,Y

The mechanism for controlling the driving of the motors 28, 44, and forreversing the direction of-vtheirr drivein determinate time relation isshown-in` detail'in Figures 4 to 14, to which attention now is directed.Mounted upon the bearing plate I8, at the left end of the apparatus is aclosed gear case 6,5into which` the terminal portion of lthe feed `screw24 extends, said terminal portion having'a gear worm 66 mounted thereon.The worm 66 is meshed with a worm gear 61 that is'mounted upon one endof a countershaft63, the latter being disposed transversely of the axisof worm 66, and journaled in the opposite lateral walls of the vgearcase 65. Mounted yupon the shaft 68 near the middle thereof is a gearworm 69 that is meshed with a worm gear 10, the latter being mountedupon a cam shaft 1|. The said cam shaft is disposed parallel to the feedscrew 24, and is journaled at onevend. in a bearing 12 in bearing plateI8, and is journaled in its medial region in a bearing-13 that ismounted in the wall of gear case 65, saidcam shaft extending throughAthe latter and having a substantial portion of its structure projectingtherefrom.

Keyed to the projecting end portion of the shaft 1I,V exteriorly of thegear case, is a hub structure 15 that is formed with a radiallyextending circumferential flange 16. Secured to the inner end face ofthehub 15 by means of a pair `of clap screws 11, 11 is a cam plate 18, saidscrews vpassing through respective arcuate slots 19,A 19inthe camplateto enable the latter to be adjusted angularly, relatively of said hub.Mounted upon the front face of cam plate 18 is a cam 39, and mountedupon the rear face thereof is a cam 6|, both of said cams projectingbeyond the periphery of the cam plate. `Said cams as shown arepositioned upon centers that are substantially 90270 apart from eachother,` but one of themis ladjustably mounted so that the said angle maybe altered to a limited extent.

The gear case 651s formed integrally with a bracket 84 that is disposedabove the cam shaft 1|, and whichcarries two electric switches thatare'in 'the electrical circuit of the reversible 4motor 28 1 andAserve'. to reverse the latter as said switches `are `operated inValternation; Said switches are of any known or desired Vconstructioncomprising` two make and two break contacts A(not shown) and areenclosed in suitable receptac1es-85, 86the switch in the former re`versing thermotor 28l when the carriage 22 isat the lright end of thescrew 2 4 Vand the switch in receptacle 86 reversingI the motor when thecar.-Y riage fis `at the voppositeend of the screw. The switch isprovided with an operating plunger 81 that is engaged with an operatinglever188 having acam 'roller B9 in its free end, said cam roller beingdisposedvin the orbit of the front cam In like manner the switch 86 isprovided with an operating plunger 90 that is engagedwith anY operatinglever 9| having a cam rollerv92 in its free end, which cam roller isdisposed in the orbit of the rear cam 8|. The cam rollers 89, 92 aredisposed substantially 26 apart with relation to the axis of camshaft1|, and this dista-nceadded tothe 270 separation of cams 80, 8| makes anangle of 296 through which the cam shaft'is required to rotate duringeach halfcycle of operation, -that is, in moving from the position shownin Figure 9 to the position shown injFigure l0 vfor example, duringwhich halfcycle the ucarriage 22-moves from one end of its traverse tothe other. This `result is accom: plished bylthe worm gears 66, 61 and69, 10 which provide a.2 50 to l reduction between the feed screw 24andV thecountershaft 1|, the pitch of the threads Lof screw 24 beingsuchv as to impel the carriage 22 substantially throughout the l lengthof its threaded portion while the counter:

and lower scraperblade 6| at determinate regions of the-carriagerstraverse, and to this end an annular cam plate 95 is mounted upon thehub 15 and `secured to the outer fa'ce of its flange 16 by cap screws 96that extend through an. arcuate slotl 91 in said hub flange to provideangular adjustability of said cam plate. Projecting laterally from theouter face of cam plate 95 is a driving stud 98 that projects through anarcuate slot 99 formed in a disc cam |00, the latter being` journaledupon a bearing I0| on the terminal end of the countershaft 1|. The slot99 is concentric with the axis of said countershaft and is in length.The stud 98 is received in one of a plurality of arcuately positionedholes 95a in the cam plate 95 (Figures 11-14). Diametrically oppositethe middle of slot 99 the periphery of the cam |00 is formed with arecessed or depressed cam surface ||0. Below the cam shaft 1| on thegear case 65 an integral bracket |02 is formed', which Ybracket carriesa receptacle or switch box |03 in which is contained an electric switch(not shown) that is in the electrical circuit of the reversible motor44. The switch is provided with an operating plunger |04 that is engagedwith anv operating lever |05 having a cam roller |06 journaled in itsfree end, said cam roller being disposed in vertical alignment with thecam shaft 1|, and urged upwardly against the periphery of cam |00; The`switch in. receptacle |03 is known` as the verticalmovement switch, andis soconstructed and arranged that when` the plunger |04 is `out orraised, as shown in the drawings, the motor lUllrotates in thedirectionthatelevates the scraper blade 6|, and when-the said plunger isin or is-depressed the motor rotates in the opposite directionV so asto-lower the scraper blade, rotation of the motor in either directioncontinung until the torquein the motor is sufficient to operate thetorque-limit relay, whereupon rotation ceases. When theV cam is. soangularly positioned that the cam roller` |06 is on the depressed camsurface ||0 thereof, the plunger |04 is in elevated position andthemotor t4V is caused to rotate in the direction that raises the blade 6|.The length of the cam surface ||01is such that the plunger |04 remainsin elevated position -while the cam |00 rotates through an angle of 43,the time interval during which said plunger is raised being suicient forthe-motor 44 to raise the blade 6| to maximum height and to stop. Thetorque that effects the stopping of motor 44, as the scraper bladeisraised, is created by the compression of spring 5l after the collar 55on screw 50 engages the lower end of lower housing 35.

As previously stated, the cam shaft v|| oscillates through an angleof-substantially 296, as does the hub 1.5 keyed thereto. Thus the stud98 projecting from the flange of said hub and through slot 99 of cam |00is adapted to oscillate the latter, but to a lesser degree, namely 156(296 minus 140.)fthe cam surface IIO -being in the medial region of the156 of cam surface that. engages the cam roller |06- during suchoscillation. At the opposite ends of cam surface I I0 are respective camsurfacesfl I I, IAI2 of greater radial extent than depression IIO, saidcam sur-l compressed, by the torque-limitv relay as prey viouslyexplained.. rIhe camsurfaces ||Il, I|2 are ofV relatively short linearvextent, andcontiguous with them are respective shallow depres-V sions orrelieved portions H3, 4 in the periphery of the cam |00. The-surfaces|I0to ||4 inclusive constituteabout 165 of the total periphery of .thecam, which, as previously stated,A oscillates through an. angle of 1569.When the cam is in such angular position that cam roller |0t is engagedwith surfaces I I3 or -I thereof, the

switchv plunger |04 vis slightlyrraised from its fully depressedposition, but not suciently to effect driving of the motor toelevate-the scraper blade. Thus there are shoulders'formed onthe cam atthe juncture of surfaces II-I, |13'` and H2, |I4 which shouldersreadilypassthecarn roller |06: when the cam isy positively driven by thestud 98; 1f, however, due to inaccurate fitting or other cause, there'issuicient -friction between the stud 98 and theV marginal "faces of slot99 to cause the stud to drive -thecam before the stud has reached theend of vthes1ot,the resistance set up by engagement of the caniroller|08 with one of the shoulders aforesaid will be sufficient to overcomesaid friction and thereby to prevent further rotation of the camuntil-the stud reaches the end of slot 99;'.

In the operationV of the apparatusfthe. millY rolls I I', I2 are set inYmotion.in;the. .usuallmanner, and a bank of rubber.v composition I4 isfed.

into the `bite of said rolls to effect the forming of a sheet or sleeveI3 of the composition upon the roll |2.` Motor 28-'is then set inmotionito operate the carriage 22, `the succeeding operationsbeing-automatically-effected and the apparatus requiring no furtherattention. As the rubber composition becomes thoroughlymixed and warmed,portions of the sleeve I3 are cut therefrom for use in other rubberworking apparatus, and as the bank of stock I4 becomesdepleted,ladditional material is thrown into the bite of the rolls.

As the motor 28 rotates, the carriage 22 moves toward one end of thescrew 24', .then reverses its direction and'moves toward the oppositeend thereof, the blade 6| rising and descending at determinater pointsAalong thetraverse of the carriage. YThe fcoursaof. the `blade `6| is=best shownin Figure 7, the arrows indicating the direction of itstravel. When the cam plate 'IB is rotating in counterclockwise directionand is in the angular position shownI in Figure 8, the blade GI is atpoint A (Figure "7) of its course, bearing against roll I2 and movingtoward the right. At thi'stirne cam |00 is 'in the position-shown inFigure 1l, the stud 98 already having moved this cam through8,1the-c'amvroller |06 still being in depression I I4 of this cam.Continuing rotation of cam |00 in counterclockwise direction bringsroller |08 onto cam surface I |70-when the scraper blade I is at pointB, Figuref7,-of its traverse, with the result the switch plunger |04rises and the switch r|03 is operatedto drive motor 44 in the directionthat raises the scraper blade, rotation of the Vmotor stopping when theblade is fully elevated. The blade continues to move laterally while inelevated position, and while the cam roller is stillengaged with camsurface |I0, the position of the latter and said cam roller as shown inFigure l2 corresponding to point C of Figure '7. Continued rotation ofcam |00 in counterclockwise direction from the position shown in Figure12 carries cam surface ||0 beyond rollerA |06, therlatter then engagingcam surface II-I Vwhich effectsthedepressing of plunger |04 andthereversing of the position of switch |03, with the result that motor 44is set in motion in the direction that lowers scraper blade 6|-, Afterthe `blade engages the mill roll I2, themotor 44! again ceases rotating,the blade being at the position shown at D, Figure '7, and the cam |00being substantially at the position shown in Figure 13, with cam roller|06 4engaging cam surface II3. 'I'he carriage 22 continues to move tothe right a short distance, until cam onlcam plate 'I8 engages andoperates switch 85,V as shown in Figure 9, thus reversing the motor 28,the `position of the carriage 22 at this time being indicated at E,Figure 7. The movement of the carriage 22 toward the ends of itstraverse may be cushionedby means of compression springs I I8, I 6mounted upon the screw 24 at the opposite ends of its threaded portion,said springs also assisting the motor in initiating the reverse movementof the carriage.

Reversing of the motor 28 turns the screw 24 inthe direction that impelsthe carriage 22 toward the left, and also reverses the direction ofrotation of cam shaft 1| so that the latter, and cam plate' 'I8 and thestud 98 then move in a clockwise direction. Stud88 moves in the slot 99,relatively of cam 00, for and engages saidcam just before the blade 6|reaches point F of its traverse, the position `of cam f |00 when theblade is at point F'being shown -in Figure 13,

The movementsof the blade '6| at the leftlendv of the machine are' thesame as those previously described atv the right end of the machineandat points G, H, I, and 5J; Figure v'7, the-'blade follows a courseidenticaltolthe course followed at points B to E, inclusive. When theblade is'at point H, the cam is substantially at the position shown inFigure 14 and moving in the direction indicated by the arrow. When theblade reaches point J, cam 8| will have moved to the positionwhere itengages cam roller 92, as shown in Figure 10, to operate switch 8E andthus to reverse the motor 28 and thereby to move the carriage 22, inreverse direction, back to position A, the point of starting.

This completes a cycle of operation, which is continuous and automaticas long as motor 28 is in operation. The apparatus is superior inperformance to similar apparatus of prior construction chiefly becauseits mechanisms are entirely electrically operated, thus obviating theuse of iiuid pressure operated devices. The use of a torque-limit relayfor stopping rotation of motor 44 obviates the use of other stopswitches and braking means, and the single spring l is utilized toprovide the torque for stopping the motor when rotating in eitherdirection.

Note that the movement, or course of the blade 6| can readily be varied.This is done by removing the nut holding the cam |00 on the shaft 1| andthen inserting another pin in another hole 95a in the cam plate 95whereby the permitted relative movement of the cam plate 18 and the cam|00 is changed and the vertical movement of the blade 6| is variedrelative to its horizontal position on the mill. Another manner in whichthe movement of the blade 6| can be changed is to substitute a differentcam for the cam |00 with the new cam having a different length arcuateslot and/or different length cam surfaces formed thereon whereby thevertical movement of the blade 6| relative to its transverse position onthe mill could be varied.

Modification may be resorted to without departing from the spirit of theinvention, or the scope thereof as defined by the appended claims.

What is claimed is:

1. In a mill of the character described, the combination of a scraperblade engageable with one of the mill rolls, a reversible feed screwhaving operative connection with the said blade for impelling itedgewise back and forth along the mill roll, a cam shaft, means foroscillating the latter through the agency of the reverse rotation of thefeed screw, a second feed screw having operative connection with thescraper blade for raising and lowering it relatively of the mill roll, areversible electric motor driving said second feed screw, a reversingstarting switch in the electric circuit of said motor, said circuitincluding a torque-limit relay for stopping the motor, and cam means onthe cam shaft for operating said starting switch after the rst mentionedfeed screw has made a determinate number of revolutions in eitherdirection.

2. A combination as defined in claim 1 including means for increasingthe torque on the motor as the blade reaches its fully raised or fullylowered positions.

3. In a mill of the character described comprising a scraper blade andmeans for moving it edgewise back and forth along a mill roll, thecombination of a member connected to said blade and movable in an up anddown direction for raising and lowering said blade relatively of themillroll, -a'motor `for moving said Vmember up and downf, 'and meansforf increasing f the torque on the motor as said memberreach'esdeterminate upper and lower limits. f

491141 a mill of the characterdescribed com privsing a s'craper'bladeand means for movingit edgewise back and forth along the mill roll, thecombination of an upright feed screw connected at its lower end to saidblade, a reversible electric motor, means connecting the motor with thefeed screw whereby the motor is enabled to effect axial movement of thefeed screw in either direction to raise and lower the screw and blade,and means for increasing the torque on the motor as the blade reachesdeterminate upper and lower limits.

5. In a mill of the character described comprising a scraper blade andmeans for moving it edgewise back and forth along the mill roll, thecombination of an upright feed screw connected at its lower end to saidblade, a reversible electric motor, means connecting the motor with thefeed screw whereby the motor is enabled to effect axial movement of thefeed screw in either direction to raise and lower the screw and blade, acompression spring moving axially with said screw, and means foreffecting compression of said spring as the screw reaches determinateupper and lower limits of movement as a means for increasing the torqueon the motor.

6. In a mill of the character described comprising a scraper blade andmeans for moving it edgewise back and forth along a mill roll, thecombination of an up and down slide to the lower end of which thescraper blade is attached, an upright feed screw having its lower endconnected to said slide and having limited axial movement relativelythereof, a compression spring mounted upon said feed screw between saidslide and a collar aiiixed to said screw, a nut engaging the upper endof said screw, and a reversible motor having driving connection withsaid nut, rotation of the latter in either direction effecting axialmovement of the screw.

7. In a mill of the character described, the combination of a scraperblade engageable with one of the mill rolls, a rotary feed screw havingoperative connection with said blade for impelling itback and forthalong said mill roll, a rotary cam shaft, speed reducing means betweensaid feed screw and said cam shaft for driving the latter, cam means onthe cam shaft for reversing the direction of rotation of the feed screwafter it has made a determinate number of revolutions, means for raisingand lowering said scraper blade relatively of the mill roll, cam

. means on the cam shaft controlling the operation of the last mentionedmeans in determinate time relation to the reversing of the feed screw,and means for effecting relative movement of the two cam means on thecam shaft.

8. A combination as defined in claim '7 in which the means for effectingrelative movement Y of the two cams consists of a lost motion drivingconnection between the cam shaft and one of the cams thereon.

9. In a mill of the character described, the combination of a scraperblade engageable with one of the mill rolls, a rotary feed screw havingoperative connection with said blade for impelling it back and forthalong said mill roll, a rotary cam shaft, speed reducing means betweensaid feed screw and said cam shaft for driving the latter, cam means onthe cam shaft for reversing the direction of rotation of the feed screwafter it scraperlbiede. operating'means being adjustable whereby thedeterminate time of operating the scraper' blade operating means withrelation to the reversing of the feed screw can be varied, and means.forv effecting; relative movement of the two cantY means on the camshaft.

' RAYMOND W. ALLEN.

